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    <title>Document</title>
    <style>
      /* 滤镜：https://developer.mozilla.org/zh-CN/docs/Web/CSS/filter */
      .box {
        width: 300px;
        height: 300px;
      }
      .blur {
        filter: blur(15px);
      }
      .grayscale {
        filter: grayscale(100%);
      }
      .grayscale:hover {
        filter: grayscale(0%);
      }
    </style>
  </head>
  <body>
    <img
      class="box"
      src="https://interactive-examples.mdn.mozilla.net/media/examples/firefox-logo.svg"
      alt=""
    />
    <img
      class="box blur"
      src="https://interactive-examples.mdn.mozilla.net/media/examples/firefox-logo.svg"
      alt=""
    />
    <img
      class="box grayscale"
      src="https://interactive-examples.mdn.mozilla.net/media/examples/firefox-logo.svg"
      alt=""
    />
  </body>
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